Method for creating customized chest response finite element model for anthropomorphic test devices involving creating finite element model for crash test dummy

ABSTRACT

A customized chest response finite element model for a crash test dummy is disclosed. A method of creating the customized chest response finite element model for the crash test dummy includes the steps of identifying two borderline sets that match with certification test data profiles for a chest of the crash test dummy, varying material properties of components of the chest for the crash test dummy, defining a mapping function and allowing intermediate sets to be interpolated from the certification test data profiles, and creating a single chest response finite element model for the crash test dummy with a user-defined input parameter for the customized chest response finite element model that defines the customized response.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of U.S. Provisional PatentApplication, Ser. No. 62/212,119, filed Aug. 31, 2015.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to crash test dummies and, moreparticularly, to a customized chest response finite element model for acrash test dummy and method of creating the customized chest responsefinite element model.

2. Description of the Related Art

Automotive, aviation, and other vehicle manufacturers conduct a widevariety of collision testing to measure the effects of a collision on avehicle and its occupants. Through collision testing, a vehiclemanufacturer gains valuable information that can be used to improve thevehicle, authorities examine vehicles to submit type approval, andconsumer organizations provide information on vehicle safety ratings tothe public.

Collision testing often involves the use of anthropomorphic testdevices, better known as “crash test dummies”, to estimate a human'sinjury risk. The dummy must possess the general mechanical properties,dimensions, masses, joints, and joint stiffness of the humans ofinterest. In addition, they must possess sufficient mechanical impactresponse similitude and sensitivity to cause them to interact with thevehicle's interior in a human-like manner.

The crash test dummy typically includes a head assembly, spine assembly(including neck), rib cage assembly, abdomen, pelvis assembly, right andleft arm assemblies, and right and left leg assemblies. Generally, therib cage assembly includes a plurality of ribs. The ribs are typicallyconnected to the spine assembly.

Currently, there is dummy-to-dummy variability seen in chest deflectionof physical test dummies in certification, sled, and vehicle testing dueto differences in materials, manufacturing, and environment. As aresult, there is a need in the art for a chest finite element model toenable users to adjust a stiffness of a thorax based on their hardwareor physical crash test dummy so as to quantify its characteristics froma thorax pendulum certification level to their sled or vehicleenvironment. There is also a need in the art for a chest finite elementmodel that not only captures a phenomenon of variability, but alsoallows users to perform robustness studies using extremes ofcertification corridors. Thus, there is a need in the art for acustomized chest response finite element model for a crash test dummyand method of creating the customized chest response finite elementmodel that meets at least one of these needs.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a customized chest responsefinite element model for a crash test dummy. The present invention alsoprovides a method of creating the customized chest response finiteelement model for a crash test dummy including the steps of identifyingtwo borderline sets that match with certification test data profiles fora chest of the crash test dummy, varying material properties ofcomponents of the chest for the crash test dummy, defining a mappingfunction and allowing intermediate sets to be interpolated from thecertification test data profiles, and creating a single chest responsefinite element model for the crash test dummy with a user-defined inputparameter for the thorax that defines the customized response.

One advantage of the present invention is that a new customized chestresponse finite element model and method is provided for a crash testdummy. Another advantage of the present invention is that the customizedchest response finite element model and method provides a customizedchest finite element model that bridges a gap between reality andsimulation by better capturing hardware behavior, and lays a frameworkfor future models applicable to other parts. Yet another advantage ofthe present invention is that the customized chest response finiteelement model and method enables users to adjust a stiffness and contactalgorithm parameters of a thorax based on their hardware test dummy soas to quantify its characteristics from the thorax pendulumcertification level to their sled or vehicle environment. Still anotheradvantage of the present invention is that the customized chest responsefinite element model and method not only captures the phenomenon ofvariability, but also allows users to perform robustness studies usingextremes of certification corridors.

Other features and advantages of the present invention will be readilyappreciated, as the same becomes better understood, after reading thesubsequent description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a crash test dummy,according to the present invention.

FIGS. 2A-2D are diagrammatic views of a customized chest response finiteelement model, according to one embodiment of the present invention, forthe crash test dummy of FIG. 1.

FIGS. 3A and 3B are elevational and perspective views of a chestpendulum impact test for the chest response finite element model ofFIGS. 2A-2D of the crash test dummy of FIG. 1.

FIGS. 4A-4C are graphical views of one example of pendulum force, forcedeflection, and chest deflection harmonized for the chest pendulumimpact test of FIG. 3.

FIGS. 5A-5C are graphical views of another example of pendulum force,force deflection, and chest deflection harmonized for the chest pendulumimpact test of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to the drawings and in particular FIG. 1, one embodiment of acrash test dummy, according to the present invention, is generallyindicated at 12. The crash test dummy 12 is of a fiftieth percentile(50%) male type and is illustrated in a seated position. This crash testdummy 12 is used primarily to test the performance of automotiveinteriors and restraint systems for front and rear seat occupants. Thesize and weight of the crash test dummy 12 are based on anthropometricstudies, which are typically done separately by the followingorganizations, University of Michigan Transportation Research Institute(UMTRI), U.S. Military Anthropometry Survey (ANSUR), and CivilianAmerican and European Surface Anthropometry Resource (CESAR). It shouldbe appreciated that ranges of motions, centers of gravity, and segmentmasses simulate those of human subjects defined by the anthropometricdata.

As illustrated in FIG. 1, the crash test dummy 12 includes a headassembly, generally indicated at 14. The crash test dummy 12 alsoincludes a spine assembly, generally indicated at 15, having an upperend mounted to the head assembly 14 and a lower end extending into atorso area of the crash test dummy 12. It should be appreciated that thespine assembly 15 includes a neck (not shown) attached to the headassembly 14.

The torso area of the crash test dummy 12 also includes a rib cage ortorso assembly, generally indicated at 16, connected to the spineassembly 15. The crash test dummy 12 also has a pair of arm assembliesincluding a right arm assembly, generally indicated at 18, and a leftarm assembly, generally indicated at 20, which are attached to the spineassembly 15 of the crash test dummy 12. It should be appreciated that anexample of a rib cage assembly 16 for a crash test dummy is disclosed inU.S. Pat. No. 9,355,575, issued May 31, 2016, the entire disclosure ofwhich is hereby expressly incorporated by reference. It should beappreciated that a lower end of the spine assembly 15 is connected to alumbar-thoracic adapter (not shown), which is connected to a lumbar topelvic adapter (not shown).

As illustrated in the FIG. 1, the crash test dummy 12 includes a pelvisassembly, generally indicated at 22, connected to the adapter. The crashtest dummy 12 also includes a right leg assembly 24 and a left legassembly 26, which are attached to the pelvis assembly 22. It should beappreciated that various components of the crash test dummy 12 may becovered in a polyvinyl skin such as a flesh and skin assembly forbiofidelity of the crash test dummy 12.

Referring to FIGS. 2A-2D, one embodiment of a single customized chestresponse finite element model 30, according to the present invention, isdisclosed for the chest or rib cage assembly 16 of the crash test dummy12. The model 30 is to be carried out on a computer system that includesa computer having a memory, a processor, a display, and a user inputmechanism, such as a mouse or keyboard (not shown). The model 30 isimplemented on the computer system in MATLAB, which is commerciallyavailable from MathWorks, coupled with other lower level languages.Efficient numerical algorithms (Genetic Algorithm) are used and coded,making it possible that a complete analysis can be done within minuteson a Pentium computer of the computer system. It should be appreciatedthat the computer system is conventional and known in the art.

As illustrated in FIGS. 2A-2D, the customized chest response finiteelement model is generally indicated at 30. As illustrated in FIG. 2A,the customized chest response finite element model 30 includes an uppermount 31 a and a lower mount 31 b. As illustrated in FIG. 2A, thecustomized chest response finite element model 30 includes a rib cageassembly 16 disposed between the upper mount 31 a and the lower mount 31b and includes a plurality of ribs 32. As illustrated in FIG. 2B, therib cage assembly 16 includes one or more ribs 32. The ribs 32 extendbetween a spine box 33 and a sternum or thorax 34. As illustrated in oneembodiment, the ribs 32 are generally arcuate and rectangular in shape,but may be any suitable shape. The ribs 32 are vertically spaced alongthe spine box 33 and thorax 34. The ribs 32 are connected to the spinebox 33 and thorax 34 by a suitable mechanism such as fasteners (notshown). Each of the ribs 32 has a general “C” shape. In the embodimentillustrated, the rib cage assembly 16 includes three different sets ofribs 32 representing nominal, soft, and stiff response for the thorax 34of the crash test dummy 12. To construct the customized chest responsefinite element model 30, all levels of chest or thorax correlation areevaluated to ensure that the response was reasonable. As illustrated inFIG. 2C, the customized chest response finite element model 30 includesthe rib cage assembly 16. As illustrated in FIGS. 2C and 2D, thecustomized chest response finite element model 30 is subjected to amodeled pendulum similar to a physical pendulum to be described. Itshould be appreciated that the chest hardware of the crash test dummy 12includes complex structural components involving ribs, bib, sternum,jacket, ensolite foam, spine box, and a transducer to measure the chestdeflection of the rib cage assembly 16 of the crash test dummy 12.

Referring to FIGS. 3A and 3B, an apparatus, generally indicated at 36,for chest pendulum impact testing pendulum impact testing for thorax orchest pendulum certification tests for the crash test dummy 12 is shown.The apparatus 36 includes a frame 38 having cables 39 for the rib cageassembly 16 of the crash test dummy 12. The apparatus 36 includes apendulum 40 pivotally connected by the cables 39 to the frame 38. Asillustrated, the pendulum 40 has one end that produces the chestdeflection of the rib cage assembly 16 as illustrated in FIG. 3A andFIG. 3B. In one embodiment, the pendulum 40 produces a chest pendulumdeflection impact test at an impact speed of 3 m/s. In anotherembodiment, the pendulum 40 produces a chest pendulum deflection impacttest at 6.7 m/s. It should be appreciated that a chest low speedcertification test for the crash test dummy 12 at 3 m/s allows for a 5mm spread in chest deflection of the rib cage assembly 16 of the crashtest dummy 12.

For creating the customized chest response finite element model 30, amethod includes the step of identifying two borderline sets (e.g., FIGS.4A-4C and 5A-5C) that matched reasonably well with the extremecertification test data profiles of the rib cage assembly 16 or chest ofthe crash test dummy 12 using the apparatus 36. The method also includesthe step of varying the material properties of key components of the ribcage assembly 16. The method may include the step of varying finiteelement contact algorithm parameters of the chest response finiteelement model 30 for components of the chest or rib cage assembly 16.The finite element contact algorithm parameters include contact frictionof the components. Then, the method includes the step of defining amapping function and allowing intermediate sets to be interpolated fromextremes; thus matching a best match to any certification could beachieved. The method further includes the step of creating a singlechest response finite element model 30 for the crash test dummy 12 witha user-defined ‘input parameter’ for the chest response finite elementmodel 30 that defines the ‘customized’ response, which is equal to thechest deflection peak seen at the certification level for the rib cageassembly 16 using the apparatus 36. The model 30 then internallycalibrates material cards of components such as the thorax 34 of the ribcage assembly 16 using a parameter script to reproduce a certificationchest deflection within 0.01 mm accuracy of a specified input. It shouldalso be appreciated that a method of material modeling for crash testdummy finite element models is disclosed in U.S. Pat. No. 9,043,187 toPang, the entire disclosure of which is hereby incorporated byreference.

The chest deflection is set between a maximum and a minimum of thecertification corridors with a default value corresponding to an averageof the certification tests of the rib cage assembly 16 for the crashtest dummy 12. In one embodiment, the chest deflection is set at amaximum of 21.5 mm and a minimum of 26.5 mm of the certificationcorridors. In another embodiment, the default value is set at 24.94 mmcorresponding to the average of the 3 m/s certification tests of the ribcage assembly 16 for the crash test dummy 12. It should be appreciatedthat a focus in development was in a chest pendulum case where there wasa larger variety of data which ensured that the finite element model 30captured a wide range of physical test dummies such as the crash testdummy 12.

As previously described, there is dummy-to-dummy variability seen in thechest deflection in physical crash test dummies (in certification, sledand vehicle tests) such as the crash test dummy 12 due to differences inmaterial, manufacturing, environment, aging effect and other factors.

As illustrated in FIGS. 4A-4C, a harmonized chest deflection, pendulumforce, and force deflection, respectively, is shown for the pendulumimpact test at 3 m/s. As illustrated in FIGS. 5A-5C, a harmonized chestdeflection, pendulum force, and force deflection, respectively, is shownfor the pendulum impact test at 6.7 m/s. The customized chest responsefinite element model 30 allows adjustment of a stiffness of componentssuch as the thorax 34 based on the physical hardware of the crash testdummy 12, which might range from stiff at one end to soft at another endof the certification corridor. It should be appreciated that a method ofmodeling dynamic response changes in anthropomorphic dummy is disclosedin U.S. Pat. No. 8,407,033 to Cooper et al., the entire disclosure ofwhich is hereby incorporated by reference. It should be appreciated thatthis customization, based on certification test data from the physicalcrash test dummy 12, enables the user to accurately quantify or predictthe chest deflection characteristics of the chest of the crash testdummy 12 at the sled or vehicular level.

The reliability of the customized chest response finite element model 30was validated across numerous component, sled and vehicle load cases.The customized chest response finite element model 30 consistentlyshowed about a 20% difference in peak chest deflection between thesoftest and stiffest thorax sets of the rib cage assembly 16 of thecrash test dummy 12. It should be appreciated that, although thecustomized chest response finite element model 30 was developed for aparticular brand of crash test dummies 12, through customization, thechest response finite element model 30 can accurately represent thedeflection for any thorax of a rib cage assembly or chest for the crashtest dummy 12.

Accordingly, the present invention is a customized chest response finiteelement model 30 that can precisely represent any physical crash testdummy 12 passing certification, thus giving better control of chestdeflection prediction. The customized chest response finite elementmodel 30 is a first of its kind model that bridges the gap betweenreality and simulation by taking variability into account. In addition,the customized chest response finite element model 30 provides theframework for future finite element models and can be applied to otherparts to better capture hardware behavior of the crash test dummy 12.

The present invention has been described in an illustrative manner. Itis to be understood that the terminology, which has been used, isintended to be in the nature of words of description rather than oflimitation.

Many modifications and variations of the present invention are possiblein light of the above teachings. Therefore, the present invention may bepracticed other than as specifically described.

What is claimed is:
 1. A method of creating a customized chest responsefinite element model for a crash test dummy, said method comprising thesteps of: identifying two borderline sets that match with certificationtest data profiles for a chest of the crash test dummy; varying materialproperties of components of the chest for the crash test dummy; defininga mapping function and allowing intermediate sets to be interpolatedfrom the certification test data profiles; and creating a single chestresponse finite element model for the crash test dummy with auser-defined input parameter for the chest response finite element modelthat defines the customized response.
 2. A method as set forth in claim1 wherein the customized response is equal to a chest deflection peakfor the chest at a certification level.
 3. A method as set forth inclaim 2 including the step of internally calibrating material cards forthe chest using a parameter script to reproduce a certification chestdeflection.
 4. A method as set forth in claim 3 wherein the chestresponse finite element model has within 0.01 mm accuracy of a specifiedinput.
 5. A method as set forth in claim 2 including the step of settingthe chest deflection between a maximum and a minimum of certificationcorridors for the crash test dummy.
 6. A method as set forth in claim 5wherein the maximum is 21.5 mm and the minimum is 26.5 mm of thecertification corridors.
 7. A method as set forth in claim 1 wherein thechest deflection is a default value corresponding to an average of 3 m/sof certification tests for the chest of the crash test dummy.
 8. Amethod as set forth in claim 7 wherein the default value is 24.94 mm. 9.A method as set forth in claim 1 including the step of varying finiteelement contact algorithm parameters of the chest response finiteelement model for components of the chest.
 10. A method as set forth inclaim 9 wherein the finite element contact algorithm parameters includecontact friction of the components.
 11. A method for a customized chestresponse finite element model for a crash test dummy, said methodcomprising the steps of: identifying two borderline sets that match withcertification test data profiles for a chest of the crash test dummy;varying material properties of components of the chest for the crashtest dummy; defining a mapping function and allowing intermediate setsto be interpolated from the data profiles; creating a single chestresponse finite element model for the crash test dummy with auser-defined input parameter for the chest response finite element modelthat defines the customized response; and internally calibratingmaterial cards for the chest using a parameter script to reproduce acertification chest deflection for the chest response finite elementmodel.
 12. A method as set forth in claim 11 wherein the customizedresponse is equal to a chest deflection peak for the chest at acertification level.
 13. A method as set forth in claim 11 wherein thechest response finite element model has within 0.01 mm accuracy of aspecified input.
 14. A method as set forth in claim 11 including thestep of setting the chest deflection between a maximum and a minimum ofcertification corridors.
 15. A method as set forth in claim 14 whereinthe maximum is 21.5 mm and the minimum is 26.5 mm of the certificationcorridors.
 16. A method as set forth in claim 11 wherein the chestdeflection is a default value corresponding to an average of 3 m/s ofcertification tests for the chest of the crash test dummy.
 17. A methodas set forth in claim 16 wherein the default value is 24.94 mm.
 18. Amethod as set forth in claim 11 including the step of varying finiteelement contact algorithm parameters of the chest response finiteelement model for components of the chest.
 19. A method as set forth inclaim 18 wherein the finite element contact algorithm parameters includecontact friction of the components.